core: Set storage type as set in the paramteres.

1) Set the storage type of the storage after it was fetched from VDSM in
GetExistingStorageDomainListQuery
2) use getStorageDomainsList to be fetched without Storage Domains type.

Change-Id: I9a6f2f22b09de9daffde5e003528324237d6835f
Bug-Url: https://bugzilla.redhat.com/1157240
Signed-off-by: Maor Lipchuk <mlipchuk@redhat.com>